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Single rotational states were populated in vibrationally excited hydrogen by stimulated Raman pumping. The population in H2 X 1∑+g(v″=0,1) and D2 X 1∑+g(v″=0,1) was probed state selectively by tunable vacuum ultraviolet (VUV) laser radiation around λ=110 nm, and the fluorescence induced when exciting the hydrogen molecules in the (0–0), (1–0), (2–0), (3–1), and (4–1) Lyman bands of the (B 1∑+u←X 1∑+g) transition monitored. From a comparison of line heights, the stimulated Raman pumping efficiency is estimated to be 30%–50% in the focal volume. Rotational transitions in X 1∑+g(v″=1) were induced in collisions with H2, D2, and He. State-to-state rotational relaxation rates were measured for the (J″=1→J″=3) transition in H2(v″=1) and for the (J″=2→J″=0,4) transitions in D2(v″=1). These rates were found to be generally higher than the corresponding previously determined ones in ground state hydrogen, in qualitative accord with recent theoretical calculations. A comparison with available theoretical state-to-state cross sections shows that the rates obtained with these cross sections are generally lower than the relaxation rates directly measured in this work. [ABSTRACT FROM AUTHOR]

Background: Bovine casein leads to an expansion of lymphocytes expressing the cutaneous lymphocyte antigen and to specific lymphocyte proliferation in a subgroup of patients with milk-responsive atopic dermatitis (AD). The casein fraction is composed of different proteins with defined and completely different sequences. Objective To define the stimulatory capacity of the major casein protein (n.Β and N) in lymphocyte proliferation assays with cells from milk-allergic and non-allergic individuals. Methods :Proliferative responses of peripheral blood mononuclear cells to lipopoly saccharide-depleted casein subfractions were measured by thymidine incorporation. Lymphocytes from milk-responsive patients with AD were compared with cells from non-responsive patients with AD and to non-atopic individuals. Atopic individuals with immediate symptoms following consumption of COW'S milk were included as positive controls. Casein-specific T-cell clones (TCC) from four patients with milk- responsive Al) were restimulated with unfractioned casein and t-casein. Results Higher proliferative responses to unfractionated casein and a-Β and &-kappa;casein were observed in milk-responsive patients compared with non-responders. Unfractionated casein and κcasein discriminated best between the milk-responsive patients with Al) and non-responders. Twenty-five of 31 TCC from patients with milk- responsive AD reacted to the mixed casein preparation and casein. Conclusion:A pronounced κ-casein -specific T-cell-mediated immune response is Found in the blood of many patients with a history of milk-related exacerbation of AD. [ABSTRACT FROM AUTHOR]

The photodissociation dynamics of A state ammonia molecules (both NH3 and ND3) has been further investigated using the technique of H(D) atom photofragment translational spectroscopy. The resulting NH2(ND2) fragments are observed to carry high levels of internal excitation, the precise disposition of which is sensitively dependent upon the parent v’2 level excited. Dissociation from the v2=0 level of the A state yields ground state NH2(ND2) fragments, primarily in their zero-point level, but with high levels of rotational excitation specifically concentrated about the a-inertial axis; the population distribution over the energetically accessible product rotational levels with N[bar_over_tilde:_approx._equal_to]Ka appears near to statistical. In contrast, dissociation from the parent v’2=1 level yields a markedly inverted fragment internal energy distribution. These different energy disposals have been rationalized via classical trajectory calculations employing the best available ab initio potential energy surfaces for the A and X states of the ammonia molecule. The energy disposal following excitation to the parent v2=2 and 3 levels is found to mimic that observed for, respectively, the v’2=0 and 1 levels. These results provide clear evidence for the importance of anharmonic coupling (whereby an even number of bending quanta are redistributed into stretching motions) in promoting the fragmentation of parent levels with v2≥2. The threshold energy for producing electronically excited NH2(A2A1) fragments is 6.02 eV [∼6.16 eV for ND2(A)]. The present studies of NH3 photolysis suggest that this fragmentation channel opens at threshold and clearly indicate that branching into this channel occurs with much higher quantum yield than hitherto believed. [ABSTRACT FROM AUTHOR]

In the THINCAT project, an alternative concept for hydrogen mitigation in a light water reactor (LWR) containment is being developed. Based on catalytic coated thermal insulation elements of the main coolant loop components, it could be considered either as an alternative to backfitting passive autocatalytic recombiner devices, or as a reinforcement of their preventive effect. The present paper summarises the results achieved at about project mid-term.Potential advantages of catalytic thermal insulation studied in the project are:

The photofragmentation dynamics of ammonia molecules following pulsed laser excitation to the two lowest levels (v’2 =0 and 1) of their A 1A‘2 excited state has been investigated by monitoring the time-of-flight spectra of the nascent H-atom products. These spectra show well resolved structure. Analysis of this structure confirms recent revised estimates of the quantity D00 (H–NH2) (4.645±0.01 eV) and reveals that the majority of the accompanying NH2 (X 2B1) fragments are formed vibrationally unexcited, but with high levels of rotational excitation specifically concentrated about the a-inertial axis. The detailed energy disposal is sensitive to the initially excited parent vibronic (and even rovibronic) level: the NH2 (X) fragments resulting from photodissociation via the v’2 =1 level of NH3 (A) carry a higher level of excitation of the N=Ka rotational levels, which show an inverted population distribution. We also describe the results of trajectory calculations employing the recently reported [M. I. McCarthy et al., J. Chem. Phys. 86, 6693 (1987)] ab initio potential energy surfaces for the A and X states of ammonia. These provide a detailed rationale for the experimentally observed energy disposal and highlight the massive influence on the eventual fragmentation dynamics of the conical intersection between these surfaces along the H–NH2 dissociation coordinate. [ABSTRACT FROM AUTHOR]